Needle-control mechanism for circular knitting machine

ABSTRACT

A rotatable cylinder, carrying on its outer periphery a set of axially reciprocable latch needles, also supports a like number of elongate selector elements each oscillatable in a respective radial plane between two off-normal positions on opposite sides of a normal position. In its off-normal positions the selector element engages either of two links which act upon the associated needle shank to control its operative displacement by a camming mechanism, either by blocking or limiting such displacement or by positively engaging the needle shank with one of two cam followers executing different strokes. The selector element is positionable, by electromagnetic or mechanical programming means, on passing through a presetting station and thereupon retains its position for the following cycle.

United States Patent [191 Allavena [451 Apr. 15, 1975 Primary ExaminerW. C. Reynolds Assistant ExaminerA. M. Falik [75] Inventor: Guido Ahvena Mflan Italy Attorney, Agent, or Firml(arl F. Ross; Herbert [73] Assignee: Semitex AG, Vaduz, Liechtenstein Dubno [22] Filed: Mar. 26, 1973 I [21] Appl. No.: 345,190 [57 ABSTRACT [30] Foreign Application Priority Data A rotatable cylinder, carrying on its outer periphery a I 2 2 set of axially reciprocable latch needles, also supports Mar. 25, 1972 Italy 2378/7 a like number of elongate selector elements each June [972 25664/72 cillatable in a respective radial plane between two off- Mar. 2, I973 Italy 2lll9/73 normal positions on pp sides of a normal p tion. In its off-normal positions the selector element 2? 66/13; engages either of two links which act upon the associ- 1 g b 8 ated needle shank to control its operative displace- [58] lem of Search g ment by a camming mechanism, either by blocking or I 5 I limiting such displacement or by positively engaging 6 R f d the needle shank with one of two cam followers exe- [5 1 e erences cuting different strokes. The selector element is posi- UNITED STATES PATENTS tionable, by electromagnetic or mechanical programl,29l,226 l/l9l9 Steed 66/13 ming means, on passing through a presetting station 8. 3 4 Sc a i 66/13 and thereupon retains its position for the following cy- 3,500,662 3/l970 Ribler 66/50 R l 3,534,566 10/1970 Farmer et al. 66/50 R FOREIGN PATENTS OR APPLICATIONS 13 Claims, 10 Drawing Figures 499,579 5/1930 Germany 66/25 R I 5 6 I 7 f4;

[A to I5 F 9 4 g i I f 8 I 7 2 I t0 1?.1' F 20. "I l2 1 552% A ii z/ PATENTEUAPR 1 ms 3', 877. 255

SHEET 1 0F 5 PATENTEU 1 51975 3.877. 255

sum 3 pg 5 ZZZ F 32E! )0, L 224 225 23 1*- i 226 H FIG 9 PROGRAMMER PATENTEDAPR 1 5197s saw u as 5 2; FnnonAuu-nc 2 Nmmcusrlc NEEDLE-CONTROL MECHANISM FOR CIRCULAR KNITTING MACHINE FIELD OF THE INVENTION My present invention relates to a circular knitting machine, e.g. as used in hosiery manufacture, in which a rotating cylinder carries a set of needles distributed over one of its peripheral surfaces (usually the outer one), these needles extending generally in the direction of the cylinder axis and being axially oscillatable between a retracted position and an extended position,

' during rotation of the cylinder, with the aid of a stationary cam track. If the cylinder is vertical and carries the needles at its top, they can be elevated by the cam track into the extended position and fall back under their own weight into the retracted position.

BACKGROUND OF THE INVENTION The movement of the needles in such a knitting machine is programmed by the configuration of the cam track. Any change in the program, designed to modify the stitch pattern, requires a stopping of the machine and a replacement of that track.

Also, diverse patterns require the positioning of the needle tips at different levels. For this purpose it has been customary to provide separate sets of low-rising and high-rising needles, but the rigidity of their programming prevents any switchover from one type of needle to the other during operation.

OBJECTS OF THE INVENTION The general object of my present invention is to provide a circular machine of this character, specifically a knitting machine for hosiery or the like, affording greater flexibility in its programming so as to permit a change in pattern during operation. A more particular object is to provide simple and effective means in such a machine for selectively varying, during operation, the strokelength of any needle in order to vary the pattern. I

SUMMARY OF THE INVENTION In accordance with the present invention, each needle is individually provided with cam-controlled actuating means for the associated needle adapted to be alternately activated and deactivated by a control mechanism, also individual thereto, carried on the rotating cylinder. This mechanism includes a selector element such as a lever which is displaceable between several discrete positions, preferably two off-normal positions.

on opposite sides ofa normal position. In one of its several positions, the selector element effectively decouples the needle from the control cam so that the needle does not carry out the oscillations otherwise programmed for it. At least once during each revolution of the cylinder, the selector element passes through a presetting station in which a programmer causes its normal or off-normal positioning, as the case may be, according to the desired type of pattern. I

According to a more specific feature of my invention, the control mechanism for each needle includes a pair of links alternately engageable by the selector element in its two off-normal positions. The first of these links limits the displacement of the needle by its actuating means in a manner enabling the oscillation thereof between its retracted position and an intermediate position, thus with a reduced stroke length; the second link intervenes in one of the two remaining positions of the selector element for either deactivating the actuating means or activating same for full-stroke oscillation of the needle between its retracted and extended positions.

In principle, then, the deactivation of a needle actuating means may occur either in the normal position of the selector element or in one of its off-normal positions. In the former instance the actuating means may include a spring urging the needle into its extended position, the spring coacting with the stationary cam track whenever such shifting of the needle is not inhibited by an off-normal setting of the selector element acting through the second link to hold the needle retracted; the first link, when displaced by the selector element in its alternate off-normal position, then blocks the advance of the needle by its spring force as soon as it reaches the intermediate position. According to the latter one of the two aforestated alternatives, the needle remains retracted unless one or the other link positively engages it, in respective off-normal positions of the selector element, with either of two cam followers oscillating with different stroke lengths; this arrangement avoids the shocks to which the needle is subjected in the first-mentioned case upon being arrested in its intermediate position.

Thus, the positioning of the selector element by the programmer upon passage of that element through the presetting station determines the mode of operation of the associated needle (immobilization, limited oscillation or full oscillation) for the following revolution or, if the system includes more than one presetting station,

for the length of its travel between two such stations.

the latter case, this element should be conductive and connectable at the presetting station to a source of direct current energizing sameas the selector element passes through a steady electromagnetic field whereby the element is displaced in one or other sense, depending upon the polarity of the energizing current. This mode of operation requires only a small expenditure of energy for each setting.

BRIEF DESCRIPTION OF THE DRAWING The above and other features of my invention will now be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 shows, in axial sectional elevation, part of a needle-carrying cylinder according to my invention together with an adjoining presetting station;

FIG. 2 is a view similar to FIG. 1, illustrating a modification;

FIG. 2A is a fragmentary diagrammatic showing of an alternate needle position in the system of FIG. 2;

FIG. 3 is a cross-sectional view taken on the line "I- III of FIG. 1',

FIG. 4 is an enlarged sectional detailed view of the area IV of FIG. 3;

FIGS. 5-8 are fragmentary elevational views of a needle-control mechanism in the system of FIG. 1, shown in four different positions; and

FIG. 9 is an elevational view of a modified presetting station for a needle-control mechanism as shown in FIG. 1 or FIG. 2.

SPECIFIC DESCRIPTION The system shown in FIGS. 1 and 3-8, forming part of an otherwise conventional and only partly illustrated circular knitting machine, comprises a cylinder 1 centered on a vertical axis (FIG. 3) and driven. continuously, by means not shown, in the direction of arrow A. The outer peripheral surface of cylinder 1 comprises an annular needle mounting 2 consisting of an array of flat, radially extending partition members 3 separated by flat spacers 4 of similar thickness but lesser radial width, these partitions and spacers defining a series of radial-plane recesses accommodating respective latch needles 5. Each spacer 4 is provided with upper and lower projections 6, 6' onto which the associated needle is held by circular springs 7, 7' common to all needles and centered on axis 0; the spring pressure is low enough to let the needle oscillate axially under the control of a respective leaf spring 9 seated in a flange 10 of the cylinder, the free end 9 of this leaf spring engaging in a recess 8 of the needle. The lower end 11 of needle 5 has the shape of a downwardly pointing arrowhead normally disposed below the level of a pair of hooks 19a, 19b at the top of two independently pivotable links 16 and 17, these links being also provided with confronting bosses a, 20b engageable by the pointed end 11 upon a reverse (i.e. downward) displacement of the needle 5 from its illustrated retracted position. Links 16 and 17, forming part of a control mechanism generally designated 15, are fulcrumed on a pair of concentric annular members 18a and 1812, respectively, which are likewise centered on cylinder axis 0. An Qshaped hairpin spring 21 bears from within upon the two links to maintain them in frictional contact .with their pivot rings 18a and 18b whereby each link retains its position in the absence of an applied external force.

The control mechanism 15 further includes an elongate selector element 22 in the form of a flat lever pivotally mounted on the outer surface of cylinder 1 with the aid of an electrically nonconductive annular spring 29, also centered on the cylinder axis 0, bearing upon an annular bolster 29' of insulating material; selector lever 22 is thereby swingable, as are links 16 and 17, in the radial plane containing the needle 5. Lever 22 is metallic and has its upper arm 22" topped by an insulating cap 22' adapted to engage the lower ends of the swingable links 16 and 17; arm 22" and the lower lever arm 22" are connected to a pair of flexible wires 32, 33 which are respectively tied to a terminal 30 and to one of a set of terminals 34 on a panel 31 rotating with the cylinder 1.

A stationary frame 12, surrounding the rotating cylinder 1, has an annular top 13 with a depending flange 14 forming a cam track. Spring extremity 9' coacts with this track 14 to raise and lower the associated needle 5 in a predetermined rhythm, throughout a revolution of the cylinder, as long as such movement is not prevented or restricted by engagement of either hook 19a, 19b with head 11. As long as selector lever 22 is in a neutral position substantially centered between links l6 and 1 7, as illustrated in FIGS. 1 and 5, the needle 5 will be free to oscillate in this manner. Upon deflection of lever 22 to the left (FIG. 6), its cap 22' engages the lower extremity 16" of link 16 whose upper extremity 16' is shorter than the corresponding extremity 17 of link 17; the resulting clockwise swing of link 16 causes its hook 19a to arrest the needle 5 in its retracted position. If, on the other hand, lever 22 is deflected clockwise (FIG. 7), its cap 22' bears upon the lower extremity 17' of link 17 whereby the latter swings counterclockwise so that its hook 19b intercepts the head 1 l of needle 5 as it rises under the action of spring 9. In this case, therefore, the vertical oscillation of needle 5 is curtailed so that its stroke is less than in the case of an unrestrained needle as shown in FIGS. 1 and S.

Toward the end of a revolution, i.e. as the needle approaches a presetting station generally designated 23 in FIGS. 1 and 3, cam track 14 descends'to a low point which depresses the spring 9 and with it the needle 5 to a level at which the pointed head 11 cammingly engages the bosses 20a and 20b of links 16 and 17 (FIG. 8), thereby restoring to its normal position whichever of these links had previously been swung toward the other by a deflection of lever 22. This returns the selector lever to a substantially undeflected position which for the sake of clarity has been illustrated as vertical though in practice it will generally be inclined to one or the other side.

Preselector station 23 comprises a horseshoe magnet, with a winding 24 and a core 24', supported by legs 25 on the peripheral wall of frame 12. Winding 24 is traversed by a steady direct current to generate a steady magnetic field giving rise to a unidirectional flux f which intersects the orbit of lever 22 around axis 0 in a limited region 26 as best shown in FIGS. 3 and 4. At the level of core 24', the cylinder 1 carries an annular array of ferromagnetic ribs 27 aligned with respective partitions 3 and alternating with nonmagnetic spacers 28, thereby defining narrow clearances to accommo date respective levers 22 with a certain radial mobility to permit their selective deflection between the limits shown in FIGS. 6 and -7. As each lever 22 rotates through a radial plane P (FIG. 4), the associated terminals 30 and 34 coplanar with that lever engage respective contacts 30' and 34' of a stationary programmer 35 for possible completion of a circuit from terminal 30 through wire 32, lever 22 and wire 33 to one of the terminals 34 whose energization, with voltage of either polarity relative to that of terminal 30, depends on a preselected program adapted to be changed during operation of the machine. According to the polarity of this energizing current, if any, the lever 22 is deflected either counterclockwise (arrow F) or clockwise (arrow F) on passing through the plane P as that current coacts with the magnetic flux f traversing the gap between ribs 27; if no current flows, it remains in its neutral position to which it has just been returned (if previously deflected) by the camming head 11 as described above with reference to FIG. 8. The several contacts 34' may be connected to different voltage sources modulated,

in the course of a cylinder revolution, according to a respectiveprogram which can be put into effect by, for example, the operation of a manual selector switch not shown. Thus, if none of these contacts carries voltage as a particular lever 22 traverses the preselection position, this lever will remain undeflected and the associated needle will execute full-stroke oscillations during the ensuing revolution; if, however, any one of these contacts is positively or negatively energized, the resulting deflection of the lever will be preserved throughout such revolution by its frictional clamping between spring 29 and bolster 29'.

In FIG. 2 we have shown a generally similar system wherein elements having counterparts in FIGS. 1 and 3-8 have been designated by the same reference numerals preceded by a l in the position of the hundreds digit. The preselector station 123 is of the same construction as station 23 and need not be described in detail. Links 116 and 117 are of equal length, their hooks 119a and 11% performing no retaining function but serving only to restore the selector lever 122 to neutral at the end of a cycle under the control of a triangular head 111 on the needle 105, as described with reference to FIG. 8. Cam track 14 has been replaced by a pair of cencentric rings 114, 114' both fixedly supported by the machine frame, the former from a nonillustrated central stem thereof and the latter from its outer peripheral wall (12 in FIG. 1). The rings 114 and 114' form respective track grooves 109, 109' in camming engagement with bosses 108, 108' ofa pair of vertically oscillating cam followers 107, 107 which are slidably guided on partition members 103 with the aid of transverse pins 110, 110'. As indicated by arrows B and B (see also FIG. 2A), the stroke of cam follower 107 determined by track 109 is substantially greater than that of cam follower 107' determined by track 109'.

An enlargement 106 on the stem of needle 105 is aligned with confronting concavities of cam followers 107 and 107 in the retracted position of that needle in which its triangular head 111 rests loosely on the hooked tips of links 116 and 117. If, now, either of these links is deflected in the manner illustrated for links 16 and 17 in FIGS. 6 and 7, the needle 105 is slightly displaced to the right or to the left (pivoting in a slot 102' of its mounting 102) so that the enlargement 106 is positively coupled with cam follower 107 or 107 as illustrated in FIG. 2A. In the former case, the needle is vertically entrained with a short oscillating stroke by the cam follower 107' for a full revolution; in the latter case it is the cam follower 107 that does the entraining so that the needle excursions are correspondingly greater. It is only when the needle is thus engaged by either cam follower that, upon its approach to presetting station 123, it is shifted downwardly beyond its illustrated retracted position to spread the camming hooks 119a; 119b for restoring the selector lever 122 to neutral.

In FIG. 9 l have shown a modified preselector station 223, suitable for use with either type of needle-control mechanism as per FIGS. 1 or 2, in which a selector level 222 passing through a predetermined angular position is mechanically displaceable by a deflecting arm 226 controlled by a programmer 235 through a pair of solenoids 234, 234'. Arm 226 acts upon a guard plate 225 which is slidably mounted in a radial clearance 227 of a flange 201 of cylinder 201, this guard plate having a slot 224 receiving the associated lever 222. Thus, as lever 222 with its individual guard plate 225 passes in its neutral position between the prongs of the arm 226, it will be shifted in the direction of arrow F or F if either the solenoid 234 or the solenoid 234' is energized at that instant by the programmer 235. An annular spring 229, which in this case could be metallic, frictionally holds an arcuately curved portion of lever 222 in Contact with a bolster 229' to maintain an established position of that lever as discussed above. Programmer 235 may also be provided with switch means for changing from one sequence of operation to another without requiring any stopping of cylinder 201.

It will be understood that the system of FIG. 1 can be readily modified to accommodate more than one intermediate needle position by the simple expedient of providing a link 16 or 17 with several vertically spaced hooks alternately engageable with head 11 at an instant when the needle has risen to a corresponding level under the control of spring 9 and cam 14.

The links 16, 17 and 116, 117 are dynamically balanced on their respective fulcra so as not to be subject to oscillations of their own during high-speed rotation of cylinder 1 or 101. Their mounting springs 21 and 121, which frictionally maintain them in a selected position, further serve to damp the shocks of adjustment, thereby preventing any rebound.

The cam tracks 114 and 114 of FIG. 2 could also be disposed on the same side of the needle array, one above the other, if one of the cam followers 107, 107 were provided with a track-engaging extension located between adjacent needles 105.

I claim:

1. In a circular knitting machine, in combination:

a cylinder mounted for rotation about its axis;

a set of needles distributed over a peripheral surface of said cylinder, said needles extending generally in the direction of said axis and being axially oscillatable between a retracted position and an extended position;

actuating means on said cylinder individual to each needle for oscillating same between said retracted and extended positions;

stationary cam means adjacent said cylinder coacting with said actuating means upon rotation of said cylinder;

mechanism on said cylinder individual to each needle for controlling the oscillation thereof by said actuating means, said mechanism including a selector element displaceable between several discrete positions including a first position wherein said actuating means operatively couples the associated needle with said cam means and a second position wherein said actuating means effectively decouples the associated needle from said cam means; and

at least one presetting station adjacent said cylinder provided with programming means effective upon passage of said selector element through said station to place the selector element in any of said discrete positions, said presetting station comprising a generator of a steady magnetic field intersecting the path of said selector element, the latter being electrically conductive and connectable at said station in an energizing circuit for the passage of a direct current therethrough under the control of said programming means with resultant displacement of said selector element from one of said discrete positions to another in a sense depending on the polarity of said direct current.

2. The combination defined in claim 1 wherein said axis is vertical, said needle being mounted at the top of said cylinder for elevation into said extended position by said actuating means upon being coupled thereto.

3. The combination defined in claim 1 wherein said selector element has a third discrete position, said mechanism including link means effective in its third position to couple the associated needle with said actuating means for oscillation thereby between said retracted position and an intermediate position.

4. The combination defined in claim 3 wherein said link means comprises a first link operatively engageable by said selector element in said third position thereof and a second link operatively engageable by said selector element in one of the other two positions thereof, said selector element being centered between said links in the remaining position thereof.

5. The combination defined in claim 4 wherein said links and said selector element are swingable in a common radial plane of said cylinder also containing the associated needle.

6. The combination defined in claim 4 wherein said links and said selector element are provided with frietional retaining means for holding same in the positions they occupy upon leaving said presetting station, each needle being reverse-displaceable by said cam means upon approaching said station and being provided with a restoring formation effective upon its reverse displacement to restore said selector element through either of said links to its centered position.

7. The combination defined in claim 4 wherein said actuating means comprises a spring engaging the associated needle and urging same into its extended position, said second link having a detent engageable with a formation on the needle to prevent its displacement by the spring force from said retracted position thereof, said first link having a detent engageable with a formation on the needle to prevent its displacement by the spring force past said intermediate position thereof.

8. The combination defined in claim 4 wherein said actuating means comprises a first cam follower oscillatable by said cam means with a relatively small axial stroke and a second cam follower oscillatable by said cam means with a relatively large axial stroke, said first link being effective to engage the needle with said first cam follower for entrainment thereby between said retracted and intermediate positions, said second link being effective to engage the needle with said second cam follower for entrainment thereby between said retracted and extended positions.

9. The combination defined in claim 1 wherein said presetting station comprises a generator of a steady magnetic field intersecting the path of said selector element, the latter being electrically conductive and connectable at said station in an energizing circuit for the passage of a direct current therethrough under the control of said programming means with resultant displacement of said selector element from a normal position in a sense depending on the polarity of said direct current.

10. The combination defined in claim 1 wherein said presetting station comprises mechanical deflector means engageable with said selector element for displacing same from a normal position in either sense under the control of said programming means.

11. In a circular knitting machine, in combination:

a cylinder mounted for rotation about its axis;

a set of needles distributed over a peripheral surface of said cylinder, said needles extending generally in the direction of said axis and being axially oscillatable between a retracted position and an extended position;

actuating means on said cylinder individual to each needle for oscillating same between said retracted and extended positions;

stationary cam means adjacent said cylinder coacting with said actuating means upon rotation of said cylinder mechanism on said cylinder individual to each needle for controlling the oscillation thereof by said actuating means, said mechanism including a selector element displaceable between several discrete positions including a first position wherein said mechanism operatively couples the associated needle with said cam means for full oscillation between said retracted and extended positions, a second position wherein said mechanism operatively couples said associated needle with said cam means for partial oscillation between said retracted position andan intermediate position, and a third position wherein said mechanism effectively decouples said associated needle from said cam means, said mechanism including a first link engageable by said selector element in one of said discrete positions and a second link engageable by said selector element in another of said discrete positions; and

at least one presetting station adjacent said cylinder provided with programming means effective upon passage of said selector element through said station to place the selector element in any of said discrete positions.

12. The combination defined in claim 11 wherein said actuating means comprises a spring engaging the associated needle and urging same into its extended position, said first link being provided with a detent engageable with a formation on the needle upon engagement of said first link by said selector element in said third position thereof to prevent a displacement of the needle by the spring force from said retracted position thereof, said second link being providedwith a detent engageable with a formation on the needle upon engagement of said second link with said selector element in said second position thereof to prevent a displacement of the needle by the spring force past said intermediate position thereof.

13. The combination defined in claim 12 wherein said links and said selector element are swingable in a common radial plane of said cylinder also containing the associated needle, said first position of said selector element lying between said second and third positions thereof. 

1. In a circular knitting machine, in combination: a cylinder mounted for rotation about its axis; a set of needles distributed over a peripheral surface of said cylinder, said needles extending generally in the direction of said axis and being axially oscillatable between a retracted position and an extended position; actuating means on said cylinder individual to each needle for oscillating same between said retracted and extended positions; stationary cam means adjacent said cylinder coacting with said actuating means upon rotation of said cylinder; mechanism on said cylinder individual to each needle for controlling the oscillation thereof by said actuating means, said mechanism including a selector element displaceable between several discrete positions including a first position wherein said actuating means operatively couples the associated needle with said cam means and a second position wherein said actuating means effectively decouples the associated needle from said cam means; and at least one presetting station adjacent said cylinder provided with programming means effective upon passage of said selector element through said station to place the selector element in any of said discrete positions, said presetting station comprising a generator of a steady magnetic field intersecting the path of said selector element, the latter being electrically conductive and connectable at said station in an energizing circuit for the passage of a direct current therethrough under the control of said programming means with resultant displacement of said selector element from one of said discrete positions to another in a sense depending on the polarity of said direct current.
 2. The combination defined in claim 1 wherein said axis is vertical, said needle being mounted at the top of said cylinder for elevation into said extended position by said actuating means upon being coupled thereto.
 3. The combination defined in claim 1 wherein said selector element has a third discrete position, said mechanism including link means effective in its third position to couple the associated needle with said actuating means for oscillation thereby between said retracted position and an intermediate position.
 4. The combination defined in claim 3 wherein said link means comprises a first link operatively engageable by said selector element in said third position thereof and a second link operatively engageable by said selector element in one of the other two positions thereof, said selector element being centered between said links in the remaining position thereof.
 5. The combination defined in claim 4 wherein said links and said selector element are swingable in a common radial plane of said cylinder also containing the associated needle.
 6. The combination defined in claim 4 wherein said links and said selector element are provided with frictional retaining means for holding same in the positions they occupy upon leaving said presetting station, each needle being reverse-displaceable by said cam means upon approaching said station and being provided with a restoring formation effective upon its reverse displacement to restore said selector element through either of said links to its centered position.
 7. The combination defined in claim 4 wherein said actuating means comprises a spring engaging the associated needle and urging same into its extended position, said second link having a detent engageable with a formation on the needle to prevent its displacement by the spring force from said retracted position thereof, said first link having a detent engageable with a formation on the needle to prevent its displacement by the spring force past said intermediate position thereof.
 8. The combination defined in claim 4 wherein said actuating means comprises a first cam follower osCillatable by said cam means with a relatively small axial stroke and a second cam follower oscillatable by said cam means with a relatively large axial stroke, said first link being effective to engage the needle with said first cam follower for entrainment thereby between said retracted and intermediate positions, said second link being effective to engage the needle with said second cam follower for entrainment thereby between said retracted and extended positions.
 9. The combination defined in claim 1 wherein said presetting station comprises a generator of a steady magnetic field intersecting the path of said selector element, the latter being electrically conductive and connectable at said station in an energizing circuit for the passage of a direct current therethrough under the control of said programming means with resultant displacement of said selector element from a normal position in a sense depending on the polarity of said direct current.
 10. The combination defined in claim 1 wherein said presetting station comprises mechanical deflector means engageable with said selector element for displacing same from a normal position in either sense under the control of said programming means.
 11. In a circular knitting machine, in combination: a cylinder mounted for rotation about its axis; a set of needles distributed over a peripheral surface of said cylinder, said needles extending generally in the direction of said axis and being axially oscillatable between a retracted position and an extended position; actuating means on said cylinder individual to each needle for oscillating same between said retracted and extended positions; stationary cam means adjacent said cylinder coacting with said actuating means upon rotation of said cylinder; mechanism on said cylinder individual to each needle for controlling the oscillation thereof by said actuating means, said mechanism including a selector element displaceable between several discrete positions including a first position wherein said mechanism operatively couples the associated needle with said cam means for full oscillation between said retracted and extended positions, a second position wherein said mechanism operatively couples said associated needle with said cam means for partial oscillation between said retracted position and an intermediate position, and a third position wherein said mechanism effectively decouples said associated needle from said cam means, said mechanism including a first link engageable by said selector element in one of said discrete positions and a second link engageable by said selector element in another of said discrete positions; and at least one presetting station adjacent said cylinder provided with programming means effective upon passage of said selector element through said station to place the selector element in any of said discrete positions.
 12. The combination defined in claim 11 wherein said actuating means comprises a spring engaging the associated needle and urging same into its extended position, said first link being provided with a detent engageable with a formation on the needle upon engagement of said first link by said selector element in said third position thereof to prevent a displacement of the needle by the spring force from said retracted position thereof, said second link being provided with a detent engageable with a formation on the needle upon engagement of said second link with said selector element in said second position thereof to prevent a displacement of the needle by the spring force past said intermediate position thereof.
 13. The combination defined in claim 12 wherein said links and said selector element are swingable in a common radial plane of said cylinder also containing the associated needle, said first position of said selector element lying between said second and third positions thereof. 